A known water pump disclosed in Japanese Patent Laid-Open Publication No. H11-336699, a body is fixed to a cylinder block with a fixing member such as bolt, a solid rotational shaft is rotatably supported by the body via a bearing, a pulley is fixed to one end of the rotational shaft via a pulley bracket with a fixing member such as bolt, an impeller is press fitted to be secured to the other end of the rotational shaft, and the impeller and the pulley are rotated as one unit. With the water pump disclosed in Japanese Patent Laid-Open Publication No. H11-336699, the rotational shaft and the pulley are provided separately and are fixed each other by the fixing member. Therefore, the number of the components of the water pump is increased and the structure thereof becomes complex.
A need thus exists for a water pump which has a simple structure while maintaining the strength of the rotational shaft.